Conventionally, a multi-plate clutch mechanism for an automatic transmission (AT), a metal belt type automatic transmission (CVT) or the like for an automobile uses a disk spring to absorb shock generated when fastening a clutch.
FIG. 18 is an enlarged sectional view of an essential part illustrating a configuration of a multi-plate clutch mechanism 100 to which a conventional disk spring 200 disclosed in Patent document 1 is applied. The multi-plate clutch mechanism 100 is provided with a clutch drum 101 forming a substantially bottomed cylindrical shape, an inner circumferential surface of which has inner splines 103 extending in an axial direction. A clutch hub 105 is concentrically arranged inside the clutch drum 101 and splines 107 are formed on its outer circumferential surface.
Between the clutch drum 101 and the clutch hub 105, outer plates 111 and inner plates 113 of a friction clutch 109 are alternately arranged. The outer plates 111 engage with the inner splines 103 of the clutch drum 101 and the inner plates 113 engage with the splines 107 of the clutch hub 105.
On one side of the friction clutch 109, a piston 117 of a hydraulic actuator 115 is arranged, on the other side thereof, a pressure plate 119 is arranged. The hydraulic actuator 115 is provided with an oil pressure chamber 121 between the piston 117 and the clutch drum 101.
Between the outer plate 111 of the friction clutch 109 and the piston 117 of the hydraulic actuator 115, a disk spring 200 is interposed. In this disk spring 200, an outer peripheral side faces the outer plate 111 of the friction clutch 109 and an inner peripheral side faces the piston 117 of the hydraulic actuator 115.
In this multi-plate clutch mechanism 100, hydraulic oil is fed to the oil pressure chamber 121 and then the piston 117 driven by oil pressure presses the outer plates 111 and the inner plates 113 of the friction clutch 109 through the disk spring 200 against the pressure plate 119.
With this pressing, the friction clutch 109 is fastened according to pressing force to control torque transmission between the clutch drum 101 and the clutch hub 105.
At this time, the disk spring 200 elastically deforms with respect to the outer plate 111 according to the pressing of the piston 117 to absorb shock generated when fastening the clutch.
A general loading characteristic of this disk spring 200 is a characteristic in which a spring constant is reduced relative to a deflection amount over a certain deflection amount as illustrated in FIGS. 19(A) and (B). Accordingly, there is a problem that the thickness of the disk spring 200 needs to be increased in order to ensure required load, thereby to cause the disk spring to be assembled into a limited space by constraint.
PATENT DOCUMENT 1: JP2008-75877A